Drug resistance is the greatest obstacle to sucessful treatment of human lung cancer, the leading cause of cancer death among men and women in the United States. Cyclosporin A has been used in preclinical and a few early clinical studies to overcome multi-drug resistance. We have shown that sensitivity to paclitaxel in non-resistant cell lines can be enhanced by CsA despite lack of expression of classical drug resistance pumps. We are using CATS and immuno-fluorescence staining to visualize microtubule assembly in cells incubated with paclitaxel and CsA. Microtubule assembly dynamics will be explored using fluorescence spectroscopy.